The invention refers to a bone plate, particularly to a small bone plate.
Usually bone plates are designed to stabilize fractural segments and to facilitate the growing together of the bone in the fracture area. It is known to build a bone plate of two parts adapted to follow a change in the length of the bone. A change of length for example may occur by a compression of the fractural segments which for example may be carried out with a specific compression device which is for example known from the German patent specifications 38 202 or 31 34 120. A change of length can also occur caused by a sintering process in the fractural region occurs or with bones of adolescent patients. It is for example known to provide two telescopically engaged bone plates with toothed portions in order to adjust a predetermined plate length. It is also known from the German patent specification 31 34 120 to locate gear means between associated plate portions for the compression of fractural bone segments. The gear means is arranged in a housing on a first plate while the output shaft of the gear means cooperates with the second plate which can be attached to the bone through a bone screw, the bone screw being inserted through an elongated hole of the first plate. Such compression means may be suitable for fractures of limbs, however, in connection with smaller bone plates, particularly in case of applications wherein a small cover of soft tissue exists, e.g. in the face or the like, the known device is not appropriate.
It is also known from the German patent specification 35 04 616 to adjust a clamping means by a threaded spindle relative to a fixedly supported clamping means. Such a device can be applied only externally, thus, cannot be applied to the facial skeleton.
Hence the object of the invention is to provide a bone plate which permits an extension or a contraction, respectively. also with smaller bone plates.
Said object is solved by the features of the claimed invention.
Satisfactorily operating small bone plates are for example known from the German utility model 87 06 912. Above all, they are designed for the application to fractures of the cranial and facial skeleton and for small fractural segments of other skeleton portions. In the known small bone plates, so-called screw hole boundaries are connected to webs, preferably at least a part of the webs having a cross-sectional surface which is equal to or smaller than twice the cross-sectional surface of the screw hole boundary. The relatively thin plates are such dimensioned that they are adapted to be deformed by the surgeon in order to conform to the bone in the region of application. It is intended to avoid a noticeable deformation of the screw hole boundaries when the plate is bent in the plane. For this, it is advantageous if the radius of a transition from the web to the screw hole boundary is dimensioned to be very small.
The bone plate according to the invention is particularly suited for the small bone plate mentioned above. The application of the invention, however, is not restricted thereto.